Mutual Separation of Gallium, Indium and Zinc Using Silica Gel Modified by a Surfactant Micelle Containing D2EHPA

Abstract

Solvent extraction is widely used as a universal method to extract and separate metals in industry. However solvent extraction has some disadvantages, for example, use of a large amount of organic solvent which could be an environmentally hazard. Therefore a solid-phase extraction method is proposed in this research. First of all, a silica gel modified with a non ionic surfactant (TritonX-100) micelle including di(2-ethylhexyl) phosphoric acid (D2EHPA) as a metal adsorbent has been prepared. The stability of the modified silica gel was examined. Next, the adsorption behavior of gallium, indium and zinc onto the modified silica gel were investigated and compared with the adsorption behavior when using silica gel alone. The amount of D2EHPA impregnated in the modified silica gel was 0.138 mmol/g-silica gel. The modified silica gel can be used as a stable adsorbent below pH 2.0 without leaking D2EHPA. The higher the pH, the higher was the extent of metal adsorbed. Gallium was adsorbed on unmodified silica gel preferentially at pH 3.0 from a mixed metal system. In contrast, indium was adsorbed onto the modified silica gel preferentially at pH 1.1 in the same system. The modified silica gel could separate the metal ions at lower pH much better than the unmodified silica gel.